1. Field of the Invention
The present invention relates to an electric power conversion apparatus that includes an inverter circuit.
2. Description of Related Art
As a conventional technology intended to increase heat dissipation efficiency of a semiconductor module by efficiently transferring heat from the semiconductor module to a cooler, patent reference literature 1 (Japanese Laid Open Patent Publication No. 2005-175163) discloses, for example, a cooling structure. According to the description of patent reference literature 1, a semiconductor module is inserted in a hole formed in a cooler for inserting a semiconductor module to allow heat to be released from a surface of the semiconductor module that abuts the hole for inserting the module. More particularly, a layer of soft metal is applied on the surface of the semiconductor module that abuts the hole for inserting the module so that heat is released to the cooler through the layer of the soft metal.
A conventional technology intended to balance the cooling efficiency and the assemblability of a semiconductor element for use in an inverter includes, for example, an inverter disclosed in patent reference literature 2. According to the description of patent reference literature 2 (Japanese Laid Open Patent Publication No. 2005-237141), an accommodating portion that accommodates a power card of which both sides of a semiconductor device are sandwiched by heat dissipation plates and a cycling path that circulates a coolant around the power card is formed, and an insulating resin is filled between the power card and the accommodating portion, and the insulating resin is cured to fix the power card.
A conventional technology for a cooling structure intended to improve cooling capacity with a decreased burden of assembling a semiconductor module is disclosed in, for example, patent reference literature 3. According to the description of patent reference literature 3 (Japanese Laid Open Patent Publication No. 2006-202899), a block is provided in which a semiconductor module is housed inside thereof and heat dissipation planes are provided on its front and rear sides to dissipate Joule heat generated in the semiconductor module. The block is inserted into a cooling water channel formed in a case so as to cause the front and rear sides of the block to face the cooling water channel.
A conventional technology of a cooling structure that is capable of cooling a smoothing capacitor as well as cooling both sides of a semiconductor module is disclosed in, for example, patent reference literature 4 (Japanese Laid Open Patent Publication No. 2001-352023). According to the description of patent reference literature 4, semiconductor modules are provided on each side of a smoothing capacitor, and a switchback-shaped flat coolant tube is used to form a coolant channel along the both sides of the semiconductor modules and along the smoothing capacitor, achieving a high level of heat dissipation efficiency without leakage.
In recent years, in automobiles, for example, various in-vehicle systems for vehicles including a drive system for a vehicle are operated electrically. In order to electrically operate the in-vehicle systems, it becomes necessary to add freshly or in place of a component of the conventional system an electrical machine that drives a driven body and an electric power conversion apparatus that controls the power supplied to a rotating electrical machine from an in-vehicle power source in order to control driving of the rotating electrical machine.
The electric power conversion apparatus, e.g. for an automobile, has functions to convert direct current power supplied from the in-vehicle power source to alternating current power for driving a rotating electrical machine and to convert alternating current power generated by the rotating electrical machine to direct current power for supplying to the in-vehicle power source. While electrical energy converted by an electric power conversion apparatus tends to increase, automobiles tend to be small in size and weight in general. Thus, increase in size and weight of an electric power conversion apparatus is limited. An in-vehicle electric power conversion apparatus, in comparison with an industrial one, is required to be used in an environment with great temperature change. Therefore, an electric power conversion apparatus relatively small in size that converts high power and assures a high level of reliability even in a high-temperature environment is required.
The electric power conversion apparatus includes an inverter circuit and performs power conversion between direct current power and alternating current power by the operation of the inverter circuit. In order to perform this power conversion, it is necessary to repeat action of switching between a blocked state and a conduction state of a power semiconductor that constitutes the inverter circuit (switching action). When the switching action is performed, a large amount of heat is generated in the power semiconductor. Because of the heat generated by a semiconductor chip, which is the power semiconductor of the inverter circuit, upon the switching action, the temperature of the semiconductor chip is increased. For this reason, it is important to prevent this temperature increase.
According as power to be converted increases, the amount of heat generated in the semiconductor chip increases. To cope with this, it is necessary to increase the size of the semiconductor chip or the number of the semiconductor chips to be used, resulting in an increase in size of the electric power conversion apparatus. As a measure of preventing such an increase in size of the electric power conversion apparatus, it is conceivable to improve cooling efficiency of the semiconductor chips.
For example, patent reference literatures 1 to 3 present proposals to increase the cooling efficiency of the semiconductor chips. Although improvement in cooling efficiency of a semiconductor chip obviously leads to miniaturization in the semiconductor chip, it does not necessarily contribute to size reduction of the overall electric power conversion apparatus. For instance, an improvement in cooling efficiency of a semiconductor chip may result in a complex structure of the overall electric power conversion apparatus. Thus, although the semiconductor chip may be miniaturized, the overall electric power conversion apparatus may not be miniaturized significantly.
Accordingly, in order to prevent an increase in size of the overall electric power conversion apparatus, it is necessary to improve the cooling efficiency of the semiconductor chip with the overall electric power conversion apparatus considered, and necessary to prevent electrical or mechanical complexity in the overall electrical power conversion apparatus. The electrical complexity results from, for example, complex electrical wiring between the semiconductor module having a semiconductor chip incorporated therein and a capacitor module, a driver board, or an alternate current connector. The mechanical complexity results from complex mounting of a semiconductor module to the channel case or complex mounting of a capacitor module.
In the technologies disclosed in the patent reference literatures 1 to 3, miniaturization of the overall electric power conversion apparatus is not sufficiently considered, and specific disclosure of the disposition of capacitor modules or the cooling structure is insufficient. The patent reference literature 4 discloses a disposition structure in which the cooling of a smoothing capacitor, in addition to the cooling of a semiconductor module, is intended. However, the disposition structure does not adopt a water-cooling method but employs a cooling method with which the semiconductor module and the smoothing capacitor are cooled through a coolant tube connected to a coolant pipe of an external refrigeration cycle device. Furthermore, an arrangement of other components such as a circuit board that is connected to the semiconductor module is not elaborated, thereby leaving an issue in miniaturization of the overall electric power conversion apparatus.
The present invention is to provide a technology for miniaturization of an overall electric power conversion apparatus. The electric power conversion apparatus according to an embodiment of the present invention described hereinafter intends to provide not only the technology for miniaturization but also improvement in reliability, productivity, and cooling efficiency, which are necessary to commercialize the device.